Question

Find the sum of first 20 terms of the sequence 178​

Answer 1

Step-by-step explanation:

where n is the number of terms, a1 is the first term and an is the last term. The sum of the first n terms of an arithmetic sequence is called an arithmetic series . Example 1: Find the sum of the first 20 terms of the arithmetic series if a1=5 and a20=62 .